Conventional bicycle wheels suffer from at least three infirmities which are known to decrease their effectiveness. These infirmities include spoke windage, weight and weight distribution.
In order to understand spoke windage, the case of a bicycle with conventional spokes moving over the ground can be considered. Spoke windage develops from the spokes of the conventional bicycle wheel as they move through the air. Taking the example of the bicycle moving at 30 mph it will be understood that the bicycle tire at the point of ground contact has no velocity relative to the ground. However, the bicycle wheel at the upward portion of the rim directly over the point of ground contact has a rim velocity twice that of the speed of the bicycle over the ground. In the case of a bicycle moving at 30 mph, this tim velocity is 60 mph. At such high rim speeds, the round spokes of a conventional bicycle wheel create much turbulence and drag resistance as they pass through the air. Indeed, the relationship of the spokes following closely one after another through the air contributes to this turbulence.
In an effort to reduce this turbulence and drag resistance, some bicyclists have attempted to stretch membranes across the rim of their bicycle wheels. These membranes cover the spokes and reduce the air drag caused by the spoke windage. This can be a satisfactory solution in limited circumstances when there is either no wind or the wind relative to the bicycle comes from directly in front of the bicycle or directly behind the bicycle. Unfortunately, when there is any wind component perpendicular to the direction of bicycle motion, the membrane acts more as a sail. The membrane in acting as a sail catches the wind creating balance and stability problems not present in the absence of the membrane. In short, in any condition of wind, the membrane detracts from the bicycle speed whenever the bicycle turns to have a wind component at an angle to the bicycle.
A second disability of conventional bicycle wheels is that of weight. A conventional bicycle wheel has a rim, a hub, and spokes all under tension extending from the rim to the hub. The spokes under tension place the rim of the bicycle in hoop compression. This hoop compression requires that the rim be strong.
The load of the bicycle and bicyclist when placed on such bicycle wheels further increases the need for rim strength. Typically, the weight of the bicycle and rider adds to the hoop compression. This addition to hoop compression occurs at the point of ground contact of the wheel. This added hoop compression is then transferred from the bottom of the wheel rim to the top of the wheel rim in hoop compression around the wheel rim. At the top of the wheel rim, the spokes, through added tension effectively hang the hub of the bicycle wheel from the top of the rim. When it is remembered that the bicycle wheel must be constructed to anticipate dynamic loadings, as where the rider hits a bump in the road, it can be seen that the rim needs to be thick and heavy relative to the rest of the wheel.
As a third disability, conventional bicycle wheels suffer from inefficient weight distribution, this inefficient weight distribution concentrating the weight at the periphery of the wheel. Where weight of the rotating bicycle wheel is concentrated at the rim, greater effort is required to change the angular velocity of the wheel. Simply stated, a bicyclist when accelerating the bicycle must expend more energy in order to have the bicycle go faster. Likewise, when brakes must be applied, the braking system extracts more energy as the bike moves from a fast speed to a slower speed.
It should be understood that where the overall weight of two wheels is the same, a wheel having weight distribution to and towards the hub is always to be preferred over a wheel having weight distribution to and towards the rim. Unfortunately, and because of the rim compression previously set forth, conventional bicycle wheels cannot have weight distribution away from the rim without becoming endangered of collapse.